/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.iotdb.db.metadata.mtree.store.disk.schemafile;

import org.apache.iotdb.commons.exception.MetadataException;
import org.apache.iotdb.commons.utils.TestOnly;
import org.apache.iotdb.db.exception.metadata.schemafile.SegmentNotFoundException;
import org.apache.iotdb.tsfile.utils.ReadWriteIOUtils;

import java.io.IOException;
import java.io.OutputStream;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;

/**
 * {@link SchemaFile} manages a collection of SchemaPages, which acts like a segment of index entry
 * {@link ISegment} or a collection of wrapped segments.
 */
public abstract class SchemaPage implements ISchemaPage {

    // All other attributes are to describe this ByteBuffer
    protected final ByteBuffer pageBuffer;

    protected int pageIndex; // only change when register buffer as a new page
    protected short spareOffset; // bound of the variable length part in a slotted structure
    protected short spareSize; // traces spare space size simultaneously
    protected short memberNum; // amount of the member, definition depends on implementation

    protected volatile boolean dirtyFlag = false; // any modification turns it true

    protected SchemaPage(ByteBuffer pageBuffer) {
        this.pageBuffer = pageBuffer;

        this.pageBuffer
                .limit(this.pageBuffer.capacity())
                .position(SchemaFileConfig.PAGE_HEADER_INDEX_OFFSET);

        pageIndex = ReadWriteIOUtils.readInt(this.pageBuffer);
        spareOffset = ReadWriteIOUtils.readShort(this.pageBuffer);
        spareSize = ReadWriteIOUtils.readShort(this.pageBuffer);
        memberNum = ReadWriteIOUtils.readShort(this.pageBuffer);
    }

    @Override
    public void syncPageBuffer() {
        this.pageBuffer.limit(this.pageBuffer.capacity());
        this.pageBuffer.position(SchemaFileConfig.PAGE_HEADER_INDEX_OFFSET);
        ReadWriteIOUtils.write(pageIndex, pageBuffer);
        ReadWriteIOUtils.write(spareOffset, pageBuffer);
        ReadWriteIOUtils.write(spareSize, pageBuffer);
        ReadWriteIOUtils.write(memberNum, pageBuffer);
    }

    ;

    @Override
    public void flushPageToChannel(FileChannel channel) throws IOException {
        this.pageBuffer.clear();
        channel.write(pageBuffer, SchemaFile.getPageAddress(pageIndex));
        dirtyFlag = false;
    }

    @Override
    public void flushPageToStream(OutputStream stream) throws IOException {
        if (pageIndex < 0) {
            // mark as check point
            stream.write(new byte[]{(byte) pageIndex});
            return;
        }

        this.pageBuffer.clear();
        stream.write(pageBuffer.array());
    }

    @Override
    public int getPageIndex() {
        return pageIndex;
    }

    @Override
    public void setPageIndex(int pid) {
        pageIndex = pid;
        this.pageBuffer.clear();
        this.pageBuffer.position(SchemaFileConfig.PAGE_HEADER_INDEX_OFFSET);
        ReadWriteIOUtils.write(pageIndex, pageBuffer);
        this.pageBuffer.clear();
    }

    @Override
    public int getSubIndex() {
        return -1;
    }

    @Override
    public void setSubIndex(int pid) {
    }

    @Override
    public ISegment<Integer, Integer> getAsInternalPage() {
        return null;
    }

    @Override
    public ISegment<String, String> getAsAliasIndexPage() {
        return null;
    }

    @Override
    public ISegmentedPage getAsSegmentedPage() {
        return null;
    }

    // for better performance when split
    @Override
    public ByteBuffer getEntireSegmentSlice() throws MetadataException {
        return null;
    }

    @Override
    public void markDirty() {
        dirtyFlag = true;
    }

    @Override
    public boolean isDirty() {
        return dirtyFlag;
    }

    @Override
    @TestOnly
    public WrappedSegment getSegmentOnTest(short idx) throws SegmentNotFoundException {
        return null;
    }

    ;

    @Override
    @TestOnly
    public void getPageBuffer(ByteBuffer dstBuffer) {
        syncPageBuffer();
        this.pageBuffer.clear();
        dstBuffer.put(this.pageBuffer);
    }
}
